The Bell Creek Granite in northern Michigan is indicated o magnetotelluric soundings as a region of extremely high apparent resistivities (over 10,000 ohm m). The tippers point toward the center of the granite. Sixty-five magnetotelluric soundings over the granite have been used to find a regional model. Soundings in the frequency range 1 to 384 Hz indicate a three-layer regional model. The highly resistive middle layer of the regional model is interpreted as the root of the Bell Creek Granite. The thickness of the resistive layer has been fit to a two-dimensional polynomial, which indicates that the thickness of the granite ranges from 12.5 to 17.5 km, increasing to the southeast.